Improved thermoelectric materials may give a push to Moores law

Heat build up in computer chips is a key factor leading to progress in chips hitting the “power wall” — blocking increases in chip speed and slowing down the doubling of chip-transistor density (Moore’s law).

One solution is thermoelectric materials, which convert heat into electricity that can be used for cooling (also used in solid-state refrigerators)*.

But progress in developing these materials has also hit a wall. That’s because materials exhibiting higher electrical conductivity but lower thermal conductivity (so the heat is not dissipated back into the chip) are not available.

Achieving this is theoretically possible by “rattling ions in cages” in crystals with complicated crystal structures, but such crystals have been hard to study.

Now an international team of scientists has discovered a solution. Led by Jon Goff from Royal Holloway, University of London, they conducted a series of experiments on crystals of sodium cobaltate, using X-ray and neutron scattering experiments carried out at the European Synchrotron Radiation Facility (ESRF) and the Institut Laue-Langevin (ILL) in Grenoble.

The experiments were able to identify specific “rattling modes” that suppress thermal conductivity by a factor of six compared to vacancy-free sodium cobaltate.

The scientists believe their approach can also be applied to other substances besides sodium cobaltate, since the approach only requires tiny crystals.